With a PCP you've got to get out of the mindset of the car's value.
Just think of it as renting, what am I getting for £xxx/month. Assume worst case of handing the car back, and if you end up with equity, then that's a bonus.
Look on Hertz's website, see how much a car will cost per month! Not quite the same I know, but the difference will more than pay for your running costs.